Type I

Depending on the phenotype the following syndromes are distinguished:


The most severe of the MPS I subtypes. Mental development of the affected children is considerably delayed, they take longer to learn to sit, sometimes they never learn to stand or walk. Language skills may be limited too. Some children can pronounce only a few words, other can learn to read a little. However, it takes very long to master those skills. Apart from common MPS features, the affected children have thick and bristled hair, thick and often joint eyebrows, often clearly hairy arms, legs and back.


The mildest form of MPS I, characterized by normal intelligence and severe physical symptoms.

It is a progressive disease affecting several organs inherited in an autosomal regressive way. The defective gene is inherited from both parents who have no signs of the disorder and causes that a child's body does not receive information as to how to build the enzyme.

The chance that a child will be affected is 25% and the chance that siblings will be afftected is 2 in 3.

Deficient enzyme: a-L-iduronidase


Since 30 September 2003 patients suffering from mucopolysaccharidosis Type I have access to long-term replacement therapy with Aldurazyme. Thanks to the replacement therapy it is possible to alleviate non-neurological symptoms of the disorder such as respiratory problems and blood circulation disorders, to improve general resistance, to reduce the size of the liver, to improve weight and growth parameters as well as reduce joint stiffness. The observable results of the treatment are related mainly to the enhanced elasticity of connective tissue. Unfortunately, the enzyme used in the replacement therapy cannot cross the blood-brain barrier which leads to the damage of the nervous system.

Without treatment patients with Hurler syndrome live into their teenage years.


© Przemysław Racinowski